1. Field of the Invention
The present invention relates to an image processing method, an image processing device and a program, and more particularly, relates to anti-counterfeit printing technology using a copy-forgery-inhibited image for deterring use of reproductions and the like.
2. Description of the Related Art
Hitherto, in order to prohibit or deter copying of documents (hereinafter, also referred to as “contents”) requiring originality thereof such as ledger sheets and certificates, these contents have been printed onto sheets subjected to special printing, called anti-counterfeit sheets. The anti-counterfeit sheets are sheets in which the original printing cannot be viewed clearly by the human eye, but a predetermined text or drawing, such as “VOID”, is manifested thereupon in the case of copying these sheets using a copier. The anti-counterfeit sheets have had problems such as the anti-counterfeit sheets needing to be subjected to special printing beforehand, resulting in an increase in cost compared to ordinary sheets, and also that only the text or drawing set at the time of manufacturing the anti-counterfeit sheets can be manifested. Techniques regarding manufacture of such anti-counterfeit sheets are disclosed in U.S. Pat. No. 5,788,285 by Wicker and U.S. Pat. No. 6,000,728 by Mowry et al.
On the other hand, while digitization of various contents have advanced, the contents requiring the originality thereof, such as ledger sheets and certificates have also been digitized. However, digitization regarding contents such as ledger sheets and certificates is still in a transitional state, and accordingly contents created by a computer are commonly output onto sheets using a printer or the like.
In addition to such a situation, techniques for fabricating sheets having the same effects as the conventional anti-counterfeit sheets using a computer and a printer have drawn considerable attention due to rapid improvement of printer performance in recent years. Techniques for overlaying contents created by using a computer with a copy-forgery-inhibited pattern image and outputting these onto sheets using a printer are disclosed in Japanese Patent Laid-Open No. 2001-197297 and Japanese Patent Laid-Open No. 2001-238075.
Though a copy-forgery-inhibited pattern image looks like a simple texture having no meaning in the original printed matter output using a printer, upon the original printed matter being copied, a predetermined text or drawing emerges over the copied matter. Thus, there is the same deterring effect for anyone attempting to copy such sheets, as with anti-counterfeit sheets.
In the event that a contents image and a copy-forgery-inhibited pattern image are overlaid and output onto sheets using a computer, normal ordinary sheets can be used for output, resulting in an advantage of cost reduction compared to the conventional anti-counterfeit sheets. Furthermore, in addition to a predetermined static text such as “VOID”, another advantage can be provided in that optional and dynamic text such as a user name, output date and time can be embedded in output sheets.
Technically speaking, copy-forgery-inhibited pattern images take advantage of the fact that the printing resolution of a printer (output device) is higher than the readable resolution of an image scanner (reading device), and a region to be detected by an image scanner and a region not to be detected by the image scanner are provided in a copy-forgery-inhibited pattern image by adjusting the dot size making up the image and the area density of a predetermined region. Subsequently, the density difference between the two regions is minimized at the stage of printed matter, and the density difference between the two regions is maximized at the stage of copied matter. In other words, while a copy-forgery-inhibited pattern image looks like a uniform texture or a simple background as viewed from human eyes since the area density difference between the two regions is minimal at the stage of printed matter, the area density difference between the two regions increases at the stage of copied matter obtained by copying the printed matter, and consequently, one region (region to be detected by the image scanner) emerges as an image that can be clearly recognized by human eyes relative to the other region.
For example, with a copy-forgery-inhibited pattern image to be printed, the image included in the region to be detected by the image scanner is made up of large dots (concentrated dots), and the image included in the region not to be detected by the image scanner is made up of isolated small dots (dispersed dots). Note that area density in the region to be detected by the image scanner is set to equal to or generally equal to that in the region not to be detected by the image scanner.
Upon the copy-forgery-inhibited pattern image thus printed being read by the image scanner and copied, while the large dots are detected by the image scanner and accordingly reproduced in copied matter, the small dots are not detected by the image scanner and accordingly mostly not reproduced in the copied matter (or only a part of the small dot is reproduced). Thus, with the copied matter, the region image made up of the small dots disappears, or the area density becomes lower than prior to copying (faded so as to become close to white). On the other hand, the region image made up of the large dots is formed as with normal scanning, and accordingly, the contrast between the two region images becomes clear.
Note that for the sake of explanation, in the following description according to the present specification, an image in a copy-forgery-inhibited pattern, of which the dots are reproduced at the time of copying, to be formed on copied matter following copying will be referred to as “latent image”, on the other hand, an image in a copy-forgery-inhibited pattern, of which dots are not reproduced at the time of copying, to disappear entirely following copying, or of which density becomes low, will be referred to as “background image”.
Also, as for a copy-forgery-inhibited pattern, a technique referred to as “camouflage” for further preventing a hidden text or image (latent image) from recognition is well known. This camouflage technique is a method for disposing a pattern of which area density is different from that in a latent image portion and background portion in a copy-forgery-inhibited pattern image on the entire copy-forgery-inhibited pattern image, and an advantage is provided wherein the camouflage pattern of which area density is different from that in the latent image portion and background portion becomes marked, the latent image becomes even more inconspicuous. Also, an advantage is obtained wherein a copy-forgery-inhibited pattern including a camouflage pattern gives a decorative impression compared to a copy-forgery-inhibited pattern image without a camouflage pattern.
The inner dots of this camouflage pattern should disappear as much as possible following copying so as to facilitate easy recognition of the latent image following copying. In the case of a simplest configuration, camouflage can be realized by preventing dots from printing at positions corresponding to the camouflage pattern.
Also heretofore, when outputting a contents image created by using a computer on a printer, printing with the layout of the contents and the output size thereof being modified can be performed. Also, a configuration wherein printed matter is generated such that contents and a copy-forgery-inhibited pattern image are not overlapped is disclosed in Japanese Patent Laid-Open No. 11-245473.
As described above, in the event of overlaying contents created by using a computer with a copy-forgery-inhibited pattern image, and outputting this, it is most important to appropriately control the size of dots to be printed, and control readability of an image scanner in a sure manner.
However, in the event that a copy-forgery-inhibited pattern image is enlarged/reduced along with the contents image, and printed in accordance with a commonly known page layout function, or enlarging/reducing processing, the contrast between the latent image and the background image increases at the time of printing, resulting in a state in which a latent image such as “VOID” that should not appear in printed matter can be recognized in some cases. Also, in some cases, a latent image may not be manifested correctly in copied matter following copying. That is to say, when a contents image to be printed is changed in size according to a change of layout and so forth, the copy-forgery-inhibited pattern image being changed in size in the same way causes the copy-forgery-inhibited pattern image to become inappropriate, and accordingly, the function thereof as a copy-forgery-inhibited pattern is sometimes lost.
For example, let us say that contents data created by using a computer is overlaid with a copy-forgery-inhibited pattern image made up of a text (latent image) of “VOID” formed with a dot pattern in a size that can be read by the image scanner of a copier, and the other portion (background) made with a dot pattern that cannot be read by the image scanner of the copier, and printed.
In the event that contents data is not changed in size, the copy-forgery-inhibited pattern image is not changed in size either. Accordingly, in this case, with printed matter just printed, an observer cannot recognize the text “VOID” in the copy-forgery-inhibited pattern image, and the observer recognizes the copy-forgery-inhibited pattern image as a simple texture or background. Upon this printed matter being copied using the copier, only the text “VOID” serving as the latent image of the copy-forgery-inhibited pattern image is manifested.
On the other hand, in the event that contents data is reduced in size and printed, the copy-forgery-inhibited pattern image is also simply reduced in size as well as the contents. Accordingly, in this case, with the copy-forgery-inhibited pattern image, the text “VOID” formed with a dot pattern in a size that can be read by the image scanner of the copier is also reduced. In other words, the number of dots per unit region is changed, or the dots themselves are reduced, due to interpolation using enlargement/reduction. Accordingly, in the event that this printed matter is copied using the copier, the image scanner cannot detect the dots of the text “VOID”, and consequently, the obtained copied matter becomes incomplete such as a case wherein the text “VOID” is dropped out from the obtained copied matter.
Also, in the event that contents data is enlarged in size and printed, a copy-forgery-inhibited pattern image is also simply enlarged in size as well as the contents. Accordingly, in this case, with the copy-forgery-inhibited pattern image, the pattern dots of the portion other than the text “VOID” formed with a dot pattern in a size that cannot be read by the image scanner of the copier is also enlarged (the number of dots per unit region is changed, or a dot itself is enlarged, due to interpolation using enlargement/reduction). Accordingly, in the event that this printed matter is copied using the copier, the image scanner detects the dots of the portion other than “VOID”, and consequently, the text “VOID” cannot be manifested on the obtained copied matter in some cases.
Furthermore, the dots making up the text “VOID” formed with a dot pattern in a size that can be read by the image scanner of the copier are also enlarged and printed in the copy-forgery-inhibited pattern image, and accordingly, the balance of area density is lost, the text “VOID” can be recognized on printed matter just printed in some cases. In this case, there is the possibility that the printed matter may be determined to be copied matter, which is incomplete as for output including a copy-forgery-inhibited pattern image.
In order to avoid such a problem, in general, even if a change of the layout or enlargement/reduction regarding contents data is specified, the enlargement or reduction of a copy-forgery-inhibited pattern image is not performed.
However, there are cases in which an operator, who intends to generate contents data to which a copy-forgery-inhibited pattern image is added, lays out the copy-forgery-inhibited pattern image according to the content of contents data and an object in some cases. For example, in the event that there is a region including a photo or logo in contents data that the operator does not intend to overlay with a copy-forgery-inhibited pattern image, the operator designs the copy-forgery-inhibited pattern image such that the copy-forgery-inhibited pattern image is not applied to that region. Also, as illustrated in FIG. 10, positions to be disposed are sometimes regulated according to the positional relation between the latent image of a copy-forgery-inhibited pattern image and a contents image.
In such a case, if an arrangement is made wherein change of the layout or enlargement/reduction regarding a contents image is performed, and also a copy-forgery-inhibited pattern image does not follow such processing, a problem occurs in which a desired output cannot be obtained. For example, as illustrated in FIG. 9, the latent image of the copy-forgery-inhibited pattern image is regulated at a specific position as to the contents image, however, if only the contents image is reduced, output is performed such as shown in FIG. 10, and this is different from the desired output.
On the other hand, if only the contents image is enlarged, output is performed such as shown in FIG. 11.